1. Field of the Invention
The present invention relates to a buckle used as a fastening device for releasably joining loose ends of belts or straps secured to various articles such as garments, bags and helmets.
2. Description of the Prior Art
One known buckle attached, for example, to opposite ends of a belt or strap is disclosed in British Patent No. 2262962. The disclosed buckle is composed of a male or plug member and a female or socket member releasably engageable with each other. The plug member includes a base and a pair of engaging legs projecting linearly from the base and having at their leading ends a pair of locking portions, respectively. The socket member has a pair of retaining portions for interlocking engagement with the locking portions of the plug member. Each of the engaging legs has an operating portion in the form of a bulged outer side flange adapted to be operated to release the locking engagement between the locking portions and the retaining portions within the socket member. The socket member has two confronting slots from which the operating portions of the engaging legs are exposed when the locking portions of the engaging legs inserted through an end opening of the socket member in the socket member are locked with the retaining portions of the socket member.
To couple the buckle, the engaging legs of the plug member are inserted into the socket member through the end opening of the latter until the locking portions of the engaging legs are locked with the retaining portions in the socket member. During that time, on progressive insertion in the socket member, the engaging legs are resiliently deflected inwardly toward each other as outer peripheral surfaces of the locking portions slidably contact with the retaining portions in the socket member. When the engaging legs are forced into the socket member until the locking portions move past the retaining portions, the inwardly deflected engaging legs are allowed to spring back to their normal undeflected position where the locking portions are locked with the retaining portions.
The prior art buckle has a drawback that the engaging legs and the operating portions which are both inserted into the socket member to interlock the locking portions and the retaining portions enlarge the size and particularly the thickness of the socket member and increase the degree of deflection of the engaging arms. In addition, since the engaging legs are formed straight and relatively rigid against lateral deflection, they are able to insure a firm engagement between the locking portion and the retaining portion with an increased coupling strength but require a relatively large force to greatly deflect the engaging legs and thus hinder smooth insertion of the plug member in the socket member. To uncouple the buckle, the operating portions must be depressed with a great force or pressure to greatly deflect the engaging legs to disengage the locking portions and the retaining portions with the result that smooth uncoupling operation is difficult to achieve. Furthermore, the engaging legs which are relatively rigid and hence inflexible, as described above, are likely to be damaged when subjected to undue pressure or force. If the rigidity of the engaging legs is lowered to facilitate the coupling and uncoupling operation of the buckle, the coupling strength between the plug member and the socket member would be reduced. Thus, the conventional buckle undergoes a mutual conflict in terms of the easiness of manipulation and the coupling strength.